docs: def get_occurrence_times_for_event(event):
      """
      Return a tuple with two sets containing the (start, end) *naive* datetimes
      of an Event's Occurrences, or the original start datetime if an
      Occurrence's start was modified by a user.
      """
      occurrences_starts = set()
      occurrences_ends = set()
      for o in event.occurrence_list:
          occurrences_starts.add(
              coerce_naive(o.original_start or o.start)
          )
          occurrences_ends.add(
              coerce_naive(o.original_end or o.end)
          )
      return occurrences_starts, occurrences_ends